RC Car - Infrared Temp Probes????

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Infrared Temp Probes????

Comments: How do I tune up a gas engine? I have a Raytek S2 non contact thermometer to tune up an OS .21RZ-B installed in an Inferno MP-6. I cannot find anywhere that explains the relation of carburation tune up vs. temperature. Which is the maximum temperature that this engine should work? If it is more than that, how to decrease it? How do I accurately tune up both the mixture control valve and the needle valve? How/where do I use the Raytek to measure the temperature?

Thank you very much...

Response: It is great that you are using an infrared temperature prop to set the air/fuel mixture on your nitro engine. This is the most accurate way of doing it. In the old days people used to set their nitro engines up by listening to the sound or looking for smoke from the pipe but these were very inconsistent methods. The use of engine temperature is far superior to maximize engine performance and reduce unwanted wear.

First things first. A basic lesson on air/fuel mixture. Generally speaking, the leaner your mixture the more power your engine will produce but the hotter it will run. The opposite is true for a richer setting, the engine will produce less power but will run cooler. To lean out the mixture you screw in the needle valve (clock wise). To richen the mixture you unscrew the needle valve (counter clockwise). This can be done to either the high end mixture or the low end mixture. For the most part, you cannot damage an engine by running it too rich but you can definitely damage an engine by running it too lean. An extremely lean mixture can damage an engine in less than one fuel tank worth of driving. This comment was written to SCARE everyone! If in doubt on the mixture, richen it.

You can change the mixture screw on both the high end and the low end. The high end adjustment screw actually adjusts the entire range of the engine (from idle to full speed) but the low end mixture only affects the low end (idle to approx. 1/4 throttle). You can alter the power band of the engine by changing the settings between the high end and the low end. For example, if you want a little more top speed but your engine is already at the correct temperature you can richen the bottom end to cool down the motor and then lean out the top end a bit to produce a higher top speed. Enough about that, I could write for hours about mixture settings. If you want a little more information, I have a few articles posted on the web. Check out "Should I Port My Nitro Engine".

Now to your specific questions. A .21 size engine will generally run between 200 and 250 degrees (Fahrenheit). Some people run them hotter but these are usually the team drivers that don't have to pay for engines so replacements are not a big deal. If you are at a big race and power is a major issue, you can lean her down a bit and bring it up over 250 degrees (say 260 or even 270) but be aware, you will be replacing the motor much sooner. (Also note, a .12 size motor will not be run as hot as a .21. As well, a touch probe such as an MIP Temp Gage will offer much different numbers than an infrared probe so you cannot use a direct comparison to the numbers offered in this answer). As I said earlier, if your engine is running too hot, you can reduce the temperature by richening the air/fuel mixture on the bottom or top end, which ever you can do without.

The temperature is taken at the glow plug. You must aim the probe down the tall cylinder head and point it directly at the glow plug (make sure it is pointing at the plug and not at the side of the heat sink head). The reason we take temperatures at the plug is because this is the only place on the engine in which the temperature is very close when compared to different engines. If you were to take the temperature at the top of the head on an engine with a small heat sink head and compare it to the temperature obtained from the top of a large heat sink head, the numbers would be completely different and you could not compare them. Also, the glow plug is the hottest point that can be externally measured on a Nitro engine.

Let's take off a few tenths per lap,

"PRO"
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